Background Respiratory function would be impaired during general anesthesia period. Researchers devoted their energies to finding effective strategies for protecting respiratory function. Low tidal volume, positive end-expiratory pressure (PEEP), and lung recruitment maneuvers (LRMs) were recommended for patients under mechanical ventilation. However, based on the current evidence, there was no consensus on whether LRMs should be routinely used for anesthetized patients with healthy lungs, and the benefits of them remained to be determined. Materials and methods To evaluate the benefits of LRMs on patients undergoing surgery with general anesthesia, we searched relevant studies in PubMed, EMBASE, Ovid Medline and the Cochrane Library up to June 30, 2018. The primary outcome was postoperative pulmonary complications (PPCs). Results Twelve trials involving 2756 anesthetized patients were included. The results of our study showed a significant benefit of LRMs for reducing the incidence of PPCs (RR = 0.67; 95%CI, 0.49 to 0.90; P<0.05; Chi 2 = 32.94, p for heterogeneity = 0.0005, I 2 = 67%). After subgroup analyses, we found LRMs combining with lung protective ventilation strategy and sustained recruitment maneuvers were associated with reducing the occurrence of PPCs. The results also revealed that the use of LRMs improved PaO 2 /FiO 2 in non-obese patients, but with extremely high heterogeneity (I 2 = 95%). Conclusion According to the findings from contemporary meta-analysis, LRMs combining with lung protective ventilation strategy may have an association with decreasing in the incidence of PPCs and improvement of oxygenation on non-obese patients. However, the conclusions must be interpreted cautiously as the outcome may be influenced dramatically due to varied LRMs and ventilation patterns.

<b><i>Background:</i></b> Lung recruitment maneuvers (LRMs) may reduce mortality and improve oxygenation in patients with acute respiratory distress syndrome (ARDS). However, the existing literature provides controversial conclusions. <b><i>Objectives:</i></b> To determine whether LRMs have benefits on ARDS patients. <b><i>Searching Methods:</i></b> We searched relevant studies in PubMed, EMBASE, Medline, and the Cochrane Library up to May 2018. We considered for inclusion all prospective and randomized controlled trials which compared LRMs and non-LRM in adult patients with ARDS. We collected data about in-hospital mortality, 28-day mortality, the length of ICU and hospital stay, PaO₂/FiO₂, and FiO₂. <b><i>Main Results:</i></b> Ten trials including 3,025 patients were analyzed. No significant difference was found in the hospital and 28-day mortality, as well as the length of ICU stay and oxygen requirement, even undergoing subgroup analysis. However, the results of this meta-analysis showed a significant benefit of LRMs for shortening the length of hospital stay (mean difference, MD = –1.75; 95% CI, –3.40 to –0.09; <i>p</i> = 0.04; <i>p</i> for heterogeneity = 0.3, <i>I</i>² = 18%) and improving PaO₂/FiO₂ ratio on the third day (MD = 52.72; 95% CI, 18.77–86.67; <i>p</i> = 0.002), but with extremely high heterogeneity (<i>p</i> for heterogeneity &#x3c;0.0001, <i>I</i>² = 99%). <b><i>Conclusion:</i></b> LRMs do not produce significant reduction of mortality in patients with ARDS but may shorten the length of hospital stay and improve oxygenation on the third day. However, the results must be interpreted cautiously as most studies were on multiple intervention exposures.

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